Efficacy of DAIR-Plus and Partial Two-Stage Exchange in Chronic Knee Megaprosthesis PJIs

Overview

This study evaluated DAIR-Plus and partial two-stage exchange (PTSE) procedures for treating chronic periprosthetic joint infections (PJI) in knee megaprostheses. Results showed these stem-retaining approaches can achieve infection control in selected patients, with outcomes influenced by host status and soft tissue conditions.

Background

Periprosthetic joint infections in megaprostheses occur at higher rates (15–40%) than in conventional total joint arthroplasties and pose significant treatment challenges due to large implant surfaces, soft tissue damage, and patient comorbidities. Acute PJIs are typically treated with DAIR, but its success is limited in megaprostheses. Chronic infections usually require implant removal via one- or two-stage revisions, which are complex and carry high risks. DAIR-Plus and PTSE, which retain well-fixed stems while removing modular components, offer less invasive alternatives that may reduce complications, especially in knee megaprostheses where soft tissue coverage and extensor mechanism preservation are critical.

Data Highlights

Key Findings

• DAIR-Plus and PTSE were applied selectively in chronic knee megaprosthesis PJIs with well-fixed stems to avoid extensive bone loss and complex reconstruction.
• Infection control was assessed at 1, 2, 5, and >5 years post-procedure, with follow-up of at least two years.
• Patient factors such as host status (McPherson classification), oncological history, and prior radiotherapy influenced outcomes.
• DAIR-Plus was often chosen when microorganisms and antibiotic sensitivities were known preoperatively, and PTSE was preferred in cases with sinus tracts or poor soft tissue conditions.
• Failure was defined as need for amputation or chronic suppressive antibiotic therapy, highlighting the severity of treatment-resistant infections.
• Patient preference and intraoperative findings also guided the choice between DAIR-Plus and PTSE.

Clinical Implications

DAIR-Plus and PTSE represent viable surgical options for managing chronic PJIs in knee megaprostheses when stems are well-fixed and patient factors are favorable. These approaches may reduce morbidity associated with full implant removal and complex reconstructions, especially in patients with compromised soft tissues or high surgical risk. Careful patient selection based on preoperative imaging, microbiology, and host status is essential to optimize outcomes.

Conclusion

Stem-retaining procedures like DAIR-Plus and partial two-stage exchange can achieve infection control in selected chronic knee megaprosthesis PJIs, offering less invasive alternatives to full implant removal. Prognostic factors and surgical judgment are critical to selecting appropriate candidates for these treatments.

References

1. International Consensus Meeting of Istanbul 2025 -- Definition and Treatment of PJI
2. McPherson et al. -- Host Status Classification
3. ICM 2018 -- PJI Diagnostic Criteria